This invention relates fluidized beds and temperature control therein. For many chemical reactions which can be carried out in a fluidized bed, there is a dependence on the reaction rate as well as the time at a specific temperature. In fact, many of these reaction rates vary exponentially with temperature. Therefore, it is desirable to be able to control temperature, powder motions and temperature profiles within the fluidized bed. In the case of production scale equipment, it is difficult to accurately control these parameters to within accepted tolerances, since the powder characteristics can change throughout the course of the reaction. This invention describes a method for controlling powder motion, establishing a temperature profile, as required, and controlling the magnitude of the temperature gradient. The present invention is an improvement on the invention described in mentioned below U.S. patent and more specifically relates to the fluidized bed.